电极肖特基接触对有机光敏晶体管性能的影响

Influence of Electrode Schottky-contacts on Performance of Organic Phototransistor

有机光敏晶体管是一种在有机场效应管结构中引入光控“栅极”的新型光探测器件,其光灵敏度、光响应度性能参数与源/漏电极和有源层的接触情况关系密切。本文通过真空蒸发法分别制备了采用金电极和铝电极的单层并五苯及酞菁铜有机光敏晶体管。研究了它们在黑暗和光照条件下的输出及转移特性。结果表明,高迁移率的并五苯有源层更适合搭配接触特性较好的金电极,该器件具有和铝电极器件相同高水平的光灵敏度~3×104,但其光响应度是铝电极器件的13倍;而低迁移率的酞菁铜薄膜较适合搭配能够和有源层形成肖特基接触的铝电极,有利于抑制暗电流、增强激子解离效率、提高光电流,进一步使器件在获得和金电极器件同数量级光响应度的同时,其光灵敏度是金电极器件的102倍。本文对光照下电极/有源层肖特基接触的能带变化做了理论分析,总结归纳了有机光敏晶体管电极材料和有源层材料的初步筛选规律。

Organic phototransistor(OPT)is made by introducing a light-controlled‘gate’into the structure of an organic field-effect transistor(OFET),which is a new type of photodetector.The performance parameters of OPTs,including photosensitivity(P)and photoresponsivity(R),are closely related to the contact between source/drain electrodes and the active layer.In this paper,a single layer of pentacene and CuPc based OPT with Au and Al electrodes were prepared by vacuum evaporation respectively.Their output and transfer characteristics in dark and under illumination were studied.The results showed that Au electrodes were more suitable for high mobility pentacene active layer with better contact characteristics.The pentacene-based OPT with Au electrodes gained the same level of P as that with Al electrodes at around 3×104,but the R of the former was 13 times higher than that of the latter.While for low mobility CuPc-based OPT,Schottky contact was formed between the Al electrode and the active layer,which was beneficial for suppressing dark current,enhancing exciton dissociation efficiency and improving photocurrent.Furthermore,the CuPc-based OPT with Al electrode obtained the same order of magnitude R as the device with Au electrode,but the P of the former was 102 times higher than the latter.The energy band variations of the electrodes/active layer Schottky contacts under illumination were discussed in this paper.And the preliminary screening rules of the electrode materials and active layer materials for OPTs were summarized.